252 SILVER. 



white colour than any of the metals. It is insipid, inodorous, and 

 not oxidated by air or moisture, but soon becomes tarnished from 

 the presence of sulphuretted hydrogen. It is much harder than 

 gold, of considerable malleability, and may be extended into leaves 

 not exceeding the ten thousandth part of an inch in thickness. 

 It melts at a high temperature, assuming a crystaline appearance 

 as it cools, and is volatalized by a very intense heat. It combines 

 with iodine, sulphur, phosphorus, and many of the metals. Silver 

 is oxidized by several of the acids, and the ozide may be easily 

 obtained, by adding lime-water to the solution of nitrate of silver, 

 and washing the precipitate. 



Salts of Silver. 



The salts of silver may be formed either by the direct action of 

 the acids on the metal, or by digesting the oxide of silver in the 

 acid with which they are to be combined. None of the salts of 

 this metal, however, except that formed with the nitric acid, are 

 employed in medicine. 



Nitrate of Silver. — The London College directs this salt to 

 be prepared by pouring one ounce of nitric acid, diluted with two 

 ounces of distilled water, on an ounce of metallic silver. A 

 violent effervescence takes takes place, and the solution proceeds 

 rapidly, especially if it be assisted by a moderate heat, acquiring 

 at the same time a temporary green colour. In this process the 

 silver decomposes a portion of the nitric acid, attracting oxygen from 

 it, attended at the same time with the evolution of a large quan- 

 tity of nitrous oxide gas ; the oxide so formed combining with 

 another portion of acid, and remaining in solution. The solution 

 should be perfectly clear and colourless ; if the silver, however, be 

 contaminated with any copper, it will have a permanent greenish 

 tint; the nitric acid must^also be very pure, for if it contains any 

 sulphuric or muriatic acids, the solution will be turbid and will 

 deposit a white powder. The metal is generally flatted into thin 

 plates, which are cut in pieces to facilitate the action of the acid ; 

 and when the solution is completed, it is evaporated to dryness. 

 The dry mass is then exposed to a gentle heat in a porcelain 

 crucible, which is gradually increased till it is fused and flows like 



